1. Field of the Invention
The invention is based on a suction jet pump.
2. Description of the Prior Art
A suction jet pump is already known from German Patent Disclosure DE 103 03 390 A1, having a drive line that discharges via a jet outlet into an intake chamber; the intake chamber has an intake opening, cooperating with a valve member, through which opening the fluid can be aspirated into the intake chamber. The valve member, together with the intake opening, forms an intake valve. The suction jet pump is driven by a driving flow that flows via the drive line. The suction jet pump is disposed in a storage tank and aspirates fuel from a fuel tank into the storage tank. At low levels in the fuel tank, it can happen that air is sometimes aspirated and conducted into the storage tank, as a result of which foaming occurs in the storage tank. However, with its large volume, the foam displaces fuel, and that can lead to a partial evacuation of the storage tank. This effect is also called dynamic leakage. A characteristic curve of the suction jet pump, representing the aspirated volumetric flow as a function of the driving flow, has a comparatively steep course. Pronounced foaming does not occur until past a critical underpressure area in the intake region of the suction jet pump, which will hereinafter be called the foam limit.
From German Patent Disclosure DE 198 28 934 A1, a suction jet pump is known, having a drive line that upstream of the jet outlet has an overpressure valve, which causes fuel, beyond a predetermined pressure, in the drive line to flow away via a valve outlet directly into the storage tank.